The invention relates to a unit for irradiating a workpiece with ultraviolet radiation, with at least one UV radiation source and at least one transporting device, it being possible by means of the transporting device for the workpiece to be fed from a charging location of the unit to an irradiating zone and to be transported from the latter to a removal location of the unit, the unit having a common charging and removal location and it being possible for the workpiece to be moved back and forth between the common charging and removal location and the irradiating zone.
Units for irradiating a workpiece with ultraviolet radiation are used, for example, in the production of interior components for motor vehicles. It is customary for them to be provided with a usually transparent layer of varnish or resin, to produce a glossy and hard-wearing surface. The layer of varnish can be applied in this case by the interior component to be coated, for example a wooden molded part, in particular a veneered part, being positioned against a wall of a molded part in such a way that a gap is formed between the wall and the surface to be coated of the interior component, which gap can subsequently be filled with liquid surface coating material which cures when exposed to ultraviolet radiation. The curing is then performed by the interior component being introduced into a unit for irradiating with ultraviolet radiation. The workpiece in the form of the interior component is then fed by means of a transporting device to an irradiating zone, i.e. the radiation field of a UV radiation source, where it is irradiated with the ultraviolet radiation. Subsequently, the workpiece is transported to a removal location of the irradiating unit, where it can be removed from the unit.
An endless transporting belt, which makes it possible for the workpiece to be transported in a straight line past one or more UV radiation sources, is usually used as the transporting device for the coating unit. Such a configuration has the advantage that a multiplicity of workpieces to be irradiated can be disposed one behind the other on the transporting belt and can be taken past the radiation sources, so that mass production can be accomplished.
However, a disadvantage of such a design is that usually a number of persons are required to operate a unit of this type.
EP-A-0 501 551 discloses a unit for the successive processing of workpieces, in which four carriers for receiving one workpiece in each case are disposed on a turntable. The turntable can be set in rotation, it being possible for the carriers, with the workpieces fixed on them, to be fed from a charging and removal location one after the other to three different workstations, in order subsequently to return to the charging and removal location. One of the workstations is formed as a UV irradiating zone. The irradiating of a workpiece by means of such a unit has been found to be time-consuming.
It is an object of the present invention to develop a unit of the type stated at the beginning in such a way that easier operation is made possible, it being possible for UV irradiation of a workpiece to be carried out within a shorter time.
This object is achieved according to the invention in the case of a unit of the generic type by the unit comprising at least two carriers for receiving one workpiece in each case, which carriers can be positioned on the transporting device and can be moved back and forth in an alternating manner between the charging and removal location and the irradiating zone.
Such a configuration has the advantage that the workpiece can be fed from the irradiating zone and, once irradiation has been performed, can be removed from the unit on the same side of the unit. The charging and removal of the workpiece can consequently be carried out by the same operator. This additionally has the advantage that the person who feeds the still unirradiated workpiece to the unit can himself check the result of the irradiation and, if need be, change the irradiating parameters of the unit for subsequent workpieces if the result of the irradiation is unsatisfactory. The operator can consequently be used not only for charging the unit and removing the workpieces but also additionally for checking the result of work and for setting the coating unit.
The configuration according to the invention also has the advantage that the unit can be formed very compactly as a single workstation. In mass production, a number of single workstations of this type can be used, so that, even if one workstation fails, overall production does not come to a standstill but instead further workpieces can be irradiated at other workstations without any interruption.
The carriers used according to the invention make it possible to align the workpiece in a defined position and feed it to the irradiating zone. For example, it may be provided that the workpiece can be securely clamped on the carrier.
To be able to irradiate as many workpieces as possible within a predetermined time, it is provided according to the invention that the unit comprises at least two carriers, which can be moved back and forth in an alternating manner between the charging and removal location and the irradiating zone. This makes it possible to dispose a first workpiece on a first carrier and then feed it to the irradiating zone. During the rradiation of this first workpiece, a second workpiece can be positioned on the second carrier and subsequently likewise be fed to the irradiating zone. Subsequently, the first workpiece can then be removed from the irradiating zone and replaced by a further workpiece.
It is particularly favorable if the carriers can be detachably connected to the transporting device. For example, it may be provided that the carriers can be screwed to or braced with the transporting device.
In the case of a preferred configuration, it is provided that the transporting device comprises at least one displaceably mounted transporting carriage. The transporting carriage may be configured, for example, in the manner of a drawer, which is displaceably held in a guide. It is of advantage here if the transporting carriage is displaceable between the charging and removal location on the one hand and the irradiating zone on the other hand.
It is particularly favorable if a number of carriers are mounted on the transporting carriage. This makes it possible to displace a number of carriers at the same time by the transporting carriage into a charging and removal position, so that a workpiece can be respectively disposed on the carriers. Subsequently, the transporting carriage is displaced into the irradiating zone, in which all the carriers disposed on the transporting carriage, with the workpieces secured on them, are exposed to the ultraviolet radiation. Once Irradiation has been performed, the transporting carriage can then be displaced back into its original position for the removal of the irradiated workpieces.
Alternatively or additionally, it may be provided that the transporting device comprises a rotatably mounted turning framework, for example a turntable. The workpieces to be irradiated can be positioned on the turning framework and subsequently transported in first instance into the irradiating zone and, once irradiation has been performed, back into the original position by turning of the turning framework.
It is of advantage here if on the turning framework there are mounted a number of carriers, which can preferably be fed by turning of the turning framework one after the other to the radiation field of a number of UV radiation sources. This permits continuous charging to and removal from the coating unit. For example, three UV radiation sources can be disposed on a common circumscribed circle, two radiation sources being disposed diametrically opposite each other and the third radiation source being positioned at an angular spacing of 90xc2x0 between the two other radiation sources. The common charging and removal location of the unit can then be disposed diametrically opposite the third radiation source. This makes it possible to transport a workpiece successively to the individual radiation sources and subsequently back again to its original position by turning the turning framework through 90xc2x0 in each case.
To protect the surroundings from ultraviolet radiation, it is of advantage if the unit comprises a covering. It can advantageously be provided here that the covering has an opening, via which the workpiece can be fed to the irradiating zone and can be removed from the unit. The opening may be provided, for example, laterally on the unit, so that the unit can be operated completely from this one side.
The coating unit can be made particularly easy to operate by making it possible for the workpieces to be fixed on the carrier and, after irradiation has been performed, removed from the carrier outside the covering and moved with the carrier through the opening. This makes it possible for the operator to secure the workpieces optimally on the carrier, without being hindered from doing so by the covering of the unit.
In the case of a particularly preferred configuration of the unit according to the invention, it is provided that the covering covers the turning framework and that the carriers are mounted displaceably on the turning framework and can be displaced through the opening. For charging the unit, it is then just necessary in each case for the turning framework to be positioned in such a way that a carrier is in line with the opening in the covering and consequently can be displaced through it.
As explained at the beginning, an irradiating unit of this type can be used in particular for the production of an internal component for motor vehicles. It is of advantage here if, for coating the workpiece and for curing the coating material by means of UV radiation, the at least one carrier comprises a molded part with a wall, against which the workpiece, that is for example the interior component, can be positioned in the region of a surface to be coated, thereby forming a gap, it being possible for the gap subsequently to be filled with liquid surface coating material which can be cured by means of UV radiation. This permits particularly cost-effective production of an interior component, for example, in that the carrier serves not only for fixing the workpiece on the transporting device, but additionally for processing the workpiece, for example its coating.